[stdlib] Silence signaling NaN in generic conversions (swiftlang#33902)

xwu · web-flow · commit 7898f0b7ad42 · 2020-09-15T15:05:29.000-04:00
diff --git a/stdlib/public/core/FloatingPoint.swift b/stdlib/public/core/FloatingPoint.swift
@@ -1897,7 +1897,8 @@ extension BinaryFloatingPoint {
 #if !os(macOS) && !(os(iOS) && targetEnvironment(macCatalyst))
     case (5, 10):
       guard #available(iOS 14.0, watchOS 7.0, tvOS 14.0, *) else {
-        self = Self._convert(from: value).value
+        // Convert signaling NaN to quiet NaN by multiplying by 1.
+        self = Self._convert(from: value).value * 1
         break
       }
       let value_ = value as? Float16 ?? Float16(
@@ -1935,7 +1936,8 @@ extension BinaryFloatingPoint {
       self = Self(value_)
 #endif
     default:
-      self = Self._convert(from: value).value
+      // Convert signaling NaN to quiet NaN by multiplying by 1.
+      self = Self._convert(from: value).value * 1
     }
   }
 

Original file line number	Diff line number	Diff line change
`@@ -1897,7 +1897,8 @@ extension BinaryFloatingPoint {`
`1897`	`1897`	`#if !os(macOS) && !(os(iOS) && targetEnvironment(macCatalyst))`
`1898`	`1898`	`case (5, 10):`
`1899`	`1899`	`guard #available(iOS 14.0, watchOS 7.0, tvOS 14.0, *) else {`
`1900`		`- self = Self._convert(from: value).value`
	`1900`	`+ // Convert signaling NaN to quiet NaN by multiplying by 1.`
	`1901`	`+ self = Self._convert(from: value).value * 1`
`1901`	`1902`	`break`
`1902`	`1903`	`}`
`1903`	`1904`	`let value_ = value as? Float16 ?? Float16(`
`@@ -1935,7 +1936,8 @@ extension BinaryFloatingPoint {`
`1935`	`1936`	`self = Self(value_)`
`1936`	`1937`	`#endif`
`1937`	`1938`	`default:`
`1938`		`- self = Self._convert(from: value).value`
	`1939`	`+ // Convert signaling NaN to quiet NaN by multiplying by 1.`
	`1940`	`+ self = Self._convert(from: value).value * 1`
`1939`	`1941`	`}`
`1940`	`1942`	`}`
`1941`	`1943`